The present invention relates to a locking device for preventing unauthorized insertion of a trailer king pin into a tractor fifth wheel coupling.
The conventional tractor-trailer hitch or coupling structure has been standardized so that practically any tractor can be coupled to any trailer. The conventional coupling structure includes a fifth wheel attached to the tractor and a downwardly extending king pin carried on the underside of the trailer, adjacent the front of the trailer. The fifth wheel is provided with a skid plate having an opening in which the king pin of the trailer is carried. The king pin has an annular groove which is engaged by movable jaws of the fifth wheel. The jaws on the fifth wheel engage the annular groove on the king pin of the trailer to pivotally secure the trailer to the tractor. When the king pin is locked into engagement with the fifth wheel, the trailer can be hauled by the tractor.
Often, when the destination of the trailer is reached, the trailer is uncoupled from the tractor to await unloading of its contents, reloading, storage or the like. There are thus many occasions when the trailers are left unattended. It is thus relatively simple for thieves to merely couple their own tractor to any unattended trailer and haul the trailer and its contents away. Such hijacking of trailers occurs frequently. Various locking means have been devised to prevent theft of trailers. For example, U.S. Pat. No. 2,554,306 granted to Mack for a "Theft Prevention Device for Tractor Drawn Trailers" discloses a king pin cover which is held to the king pin by the latch arm of a locking unit. U.S. Pat. No. 2,641,124 granted to Gallagher et al. for a "Lock for Fifth Wheel King Pins" discloses a king pin cover which is held to the king pin by a conventional padlock. U.S. Pat. No. 3,269,159 granted to Young for a "Theft Prevention Device for Trailers" discloses a hinged king pin cover having two ends which lock together.
Prior king pin locks, including those disclosed above have several disadvantages. Particularly, prior lock collar designs are generally not strong enough to resist a heavy blow from a sledge, for example, without being broken and thus, rendered useless. Other designs have required costly parts or are expensive to manufacture. Still other collar designs are difficult to install and remove by the user.